Semaglutide (Ozempic, Wegovy): research, side effects and approved dosing
In short
Semaglutide is a prescription medicine acting on the GLP-1 receptor, with an EU marketing authorisation for type 2 diabetes and obesity under the brand names Ozempic, Wegovy and Rybelsus [4, 7, 8]regulator. In large randomised trials it lowered body weight and reduced cardiovascular events [1, 3]A.
- Ozempic, Wegovy and Rybelsus contain the same active substance, semaglutide. Ozempic and Rybelsus are authorised for type 2 diabetes, Wegovy for weight management [4, 7, 8]regulator.
- In the STEP 1 trial body weight fell by a mean of 14.9% over 68 weeks with semaglutide and 2.4% with placebo [1]A.
- When the medicine was stopped, about two thirds of the lost weight came back within a year [9]A.
- The most common side effects are nausea, diarrhoea, vomiting and constipation [1]A [4]regulator.
- In Finland semaglutide is a medicine available only on prescription [4]regulator [6]regulator. It is not on the WADA Prohibited List [16]regulator.
What is semaglutide?
Semaglutide is a modified version of the human hormone GLP-1 (glucagon-like peptide 1). It binds the same receptor as the body's own GLP-1, but it acts for much longer [12]official.
Which is which in the EU:
- Ozempic (semaglutide): a once-weekly injection under the skin for type 2 diabetes in adults. EU authorisation 8 Feb 2018 [7]regulator.
- Rybelsus (semaglutide): a once-daily tablet for type 2 diabetes in adults. EU authorisation 3 Apr 2020 [8]regulator.
- Wegovy (semaglutide): a weight management medicine. It comes as a once-weekly injection pen and as a once-daily tablet; the tablet is for adults only. EU authorisation 6 Jan 2022 [4]regulator.
All three are available only on prescription [4, 7, 8]regulator. Semaglutide is an authorised medicine, not a research chemical. A product bought online "for research use" is not the same thing as the pharmacy medicine [5]regulator. Other GLP-1 medicines and how they differ: Weight-loss drugs and GLP-1. All substances: Peptides A-Z.
Evidence at a glance
Each cell gives the kind of study and its source. The letter is the evidence level, not the result.
| Claimed effect | Humans | Animals | Cells |
|---|---|---|---|
| Weight loss (obesity) | STEP 1: 1,961 adults, -14.9% vs -2.4% on placebo over 68 weeks [1]A | - | - |
| Cardiovascular events | SELECT: 17,604 people, 6.5% vs 8.0% [3]A; SUSTAIN-6 in diabetes 6.6% vs 8.9% [2]A | - | - |
| Keeping the weight off | Those who continued kept losing, those switched to placebo regained 6.9% [10]A; after stopping about 2/3 came back within a year [9]A | - | - |
| Type 2 diabetes (blood glucose) | Authorised indication [7, 8]regulator; SURPASS-2: HbA1c fell 1.86 percentage points with 1 mg [15]A | - | - |
| Compared with tirzepatide | SURMOUNT-5: -13.7% with semaglutide vs -20.2% with tirzepatide, open-label [14]A | - | - |
| Safety | Gut symptoms common; in SELECT 16.6% vs 8.2% stopped because of adverse events [3]A | - | - |
"-" = no such study is known. The evidence for an authorised medicine comes from human trials, so the animal and cell columns are empty.
What is semaglutide used for?
In the EU semaglutide is used for two authorised purposes: type 2 diabetes (Ozempic, Rybelsus) and weight management (Wegovy) [4, 7, 8]regulator.
- Type 2 diabetes: for adults whose diabetes is not sufficiently controlled [7, 8]regulator.
- Weight management: for adults with obesity, or with overweight plus a weight-related health problem, and for adolescents from 12 years of age under set conditions [4]regulator.
- Heart and blood vessels: in the SELECT trial semaglutide reduced cardiovascular events in people with cardiovascular disease and overweight but without diabetes [3]A.
According to the EMA, semaglutide regulates appetite: it increases the feeling of fullness and reduces hunger and food intake [4]regulator. Cost, reimbursement by Kela (Finland's social insurance institution) and getting a prescription: Weight-loss drug cost and prescription.
How does semaglutide work?
Semaglutide acts like the body's own GLP-1 hormone: it binds the GLP-1 receptor [12]official. According to the EMA it helps regulate appetite by increasing fullness and reducing hunger and food intake [4]regulator.
The body's own GLP-1 breaks down quickly, but semaglutide has a half-life of about one week [12]official. That is why one injection a week is enough [1, 3]A.
Has semaglutide been studied in humans?
Yes, extensively. Semaglutide has several placebo-controlled phase 3 trials with thousands of participants [1, 2, 3]A. This sets it apart from most substances on this site, which have mainly animal studies.
The key trials
- STEP 1 (2021). 1,961 adults with obesity or overweight but without diabetes received semaglutide or placebo for 68 weeks alongside lifestyle intervention. Body weight fell by a mean of 14.9% in the semaglutide group and 2.4% in the placebo group [1]A.
- SUSTAIN-6 (2016). 3,297 people with type 2 diabetes at high cardiovascular risk were followed for two years. Cardiovascular death, heart attack or stroke occurred in 6.6% of the semaglutide group and 8.9% of the placebo group [2]A.
- SELECT (2023). 17,604 people with cardiovascular disease and overweight or obesity but without diabetes were followed for a mean of about 40 months. The same composite event occurred in 6.5% of the semaglutide group and 8.0% of the placebo group [3]A.
- STEP 4 (2021). 803 adults first took semaglutide for 20 weeks and lost a mean of 10.6% of body weight. They were then randomly assigned to continue or switch to placebo for 48 weeks. Those who continued lost a further 7.9%, while those switched to placebo regained 6.9% [10]A.
What happens when the medicine is stopped
In the STEP 1 extension, 327 participants were followed for one year after both the medicine and the lifestyle intervention ended. The semaglutide group had lost a mean of 17.3% of body weight over 68 weeks. One year later 11.6 percentage points had come back, about two thirds, leaving a net loss of 5.6% from the start. Most cardiovascular and metabolic measures moved back towards baseline. All extension analyses were exploratory [9]A.
These are group-level results. An individual's result can differ, and the results do not transfer to a product bought online.
Who studies semaglutide?
Most of the semaglutide trials were funded by the manufacturer, Novo Nordisk. STEP 1, SUSTAIN-6 and SELECT were funded by the manufacturer [1, 2, 3]A, and some authors of the STEP 1 extension and STEP 4 were employed by Novo Nordisk [9, 10]A. SURMOUNT-5 and SURPASS-2, which compared semaglutide with tirzepatide, were funded by the maker of the competing medicine tirzepatide [14, 15]A.
Who wrote this page: the editorial team
This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.
How long does semaglutide stay in the body?
Semaglutide has a half-life of about one week [12]official. That is why injected semaglutide is given once a week [1, 3]A, while the tablet is taken once a day [4, 8]regulator.
Absorption from the tablet varies more than from the injection, so the effect of switching from the injection to the tablet cannot easily be predicted [12]official.
What are the side effects of semaglutide?
The most common side effects are gut symptoms: nausea, diarrhoea, vomiting, constipation and abdominal pain. According to the EMA, these and headache affect more than 1 in 10 people taking Wegovy (semaglutide) [4]regulator.
What users report. In the Reddit accounts we compiled (not research), 711 of 1345 people (53%) reported some harm, most often: nausea (212, 16%), stomach pain or bloating (120, 9%) and vomiting (95, 7%). People tend to post when something goes wrong, so this share does not tell how common harms are. Semaglutide is a prescription medicine. The figures describe users' experiences, not treatment advice: we did not record doses, dose changes, where the medicine came from or how much weight was lost. Of those who said how they took it, 744 injected it and 77 took it as tablets. The harms in detail: Semaglutide user experiences.
What the trials reported
- STEP 1: the most common harms were nausea and diarrhoea, typically transient and mild to moderate. 4.5% of the semaglutide group and 0.8% of the placebo group stopped treatment because of gut symptoms [1]A.
- SELECT: an adverse event led to permanent discontinuation in 16.6% of the semaglutide group and 8.2% of the placebo group [3]A.
- STEP 4: gut symptoms were reported by 49.1% of those who continued semaglutide and 26.1% of those switched to placebo [10]A.
- Heartburn: reflux is a common side effect of Wegovy (semaglutide), affecting up to 1 in 10 people. Indigestion and burping are also common [12]official.
Eyes
In SUSTAIN-6, retinopathy complications of diabetes were more frequent in the semaglutide group than in the placebo group (hazard ratio 1.76) [2]A. According to the EMA, serious worsening of diabetic retinopathy is common with Ozempic (semaglutide), meaning it may affect up to 1 in 10 people, and the risk also applies to the Rybelsus tablet [7, 8]regulator.
The Wegovy product information warns about NAION, a disorder of the blood supply to the optic nerve. In population studies semaglutide in adults with type 2 diabetes was linked to about a two-fold relative risk, corresponding to about one extra case per 10,000 person-years of treatment. It is classed as very rare. A sudden loss of vision calls for an eye examination [12]official.
Pancreas and gallbladder
According to the Wegovy summary of product characteristics, acute pancreatitis has been seen with GLP-1 medicines. It is an uncommon side effect, affecting up to 1 in 100 people. The typical sign is severe, long-lasting stomach pain that may spread to the back, which needs a doctor straight away. If pancreatitis is suspected, semaglutide is stopped, and it is not restarted if pancreatitis is confirmed [12]official.
Gallstones are a common side effect, affecting up to 1 in 10 people. In trials they were reported in 1.6% of people on semaglutide and 1.1% on placebo [12]official.
Low blood sugar
According to the EMA, low blood sugar is among the most common side effects of the Rybelsus tablet (semaglutide) (more than 1 in 10 people) when it is used with insulin or a sulphonylurea [8]regulator. More: Side effects and safety.
Interactions and who lacks data
The main known interaction is the risk of low blood sugar with insulin or a sulphonylurea [8]regulator. Semaglutide slows stomach emptying, so it is used with caution alongside oral medicines that need to be absorbed quickly. In people taking warfarin or another coumarin, INR is monitored frequently after semaglutide is started [12]official.
Pregnancy and breastfeeding. Semaglutide is not used during pregnancy or breastfeeding. According to the summary of product characteristics, it is stopped at least two months before a planned pregnancy, because it leaves the body slowly. Women who could become pregnant are advised to use contraception during treatment [12]official.
- Experience in people over 85 and in severe kidney or liver impairment is limited [12]official.
- Wegovy (semaglutide) tablets have not been studied under 18 years of age [4]regulator [12]official.
- There were not enough data to judge how well injected Wegovy works in adolescents who are overweight but not obese [4]regulator.
What speaks against it and what is unknown
The effect is well shown, but it lasts only as long as the medicine is taken: after stopping, most of the weight came back [9]A [10]A.
Counter-evidence
- After stopping, about two thirds of the lost weight returned within a year, and cardiovascular and metabolic measures moved back towards baseline [9]A.
- In SELECT about twice as many people stopped because of adverse events as in the placebo group [3]A.
- In a head-to-head trial tirzepatide lowered body weight more than semaglutide [14]A.
- The main trials were funded by the manufacturer [1, 2, 3]A.
What the evidence does not support
- "Ozempic and Wegovy are different active substances": both contain the same semaglutide. Ozempic is authorised for type 2 diabetes and Wegovy for weight management [4, 7]regulator.
- "Once the weight is off, you can stop and the result stays": in the STEP 1 extension about two thirds came back within a year [9]A, and in STEP 4 those switched to placebo regained 6.9% [10]A.
- "Semaglutide bought online for research use is the same as the pharmacy medicine": according to Fimea, a "for research use only" product is not intended for humans [5]regulator. The FDA has warned companies that sold semaglutide with such labels and is also aware of counterfeit Ozempic [11]regulator.
What is not known
- Weight after stopping was followed in the STEP 1 extension for only one year, and the analyses were exploratory [9]A.
- Wegovy tablets have not been studied in adolescents [4]regulator.
Semaglutide dosage in studies
Semaglutide has an approved dosing schedule, and the dose is always decided by the prescriber. Below are first the doses used in trials and then the approved dosing from the product information, as stated there. Neither is advice for your own use.
| Study | Who | Dose and route | Duration |
|---|---|---|---|
| STEP 1 (2021) | 1,961 adults, obesity or overweight, no diabetes | 2.4 mg under the skin once a week | 68 weeks [1]A |
| SUSTAIN-6 (2016) | 3,297 people with type 2 diabetes | 0.5 mg or 1.0 mg under the skin once a week | 104 weeks [2]A |
| SELECT (2023) | 17,604 people, cardiovascular disease and overweight | 2.4 mg under the skin once a week | mean about 40 months [3]A |
| STEP 4 (2021) | 803 adults | raised over 16 weeks to 2.4 mg a week, then 2.4 mg a week | 20 + 48 weeks [10]A |
| SURMOUNT-5 (2025) | 751 adults, obesity, no diabetes | maximum tolerated dose of 1.7 or 2.4 mg once a week | 72 weeks [14]A |
| SURPASS-2 (2021) | 1,879 people with type 2 diabetes | 1 mg once a week | 40 weeks [15]A |
Approved dosing. According to the product information, the dose of the Wegovy injection (semaglutide) is raised over 16 weeks to 2.4 mg a week, and for adults there is also a 7.2 mg strength. The maintenance dose of the Wegovy tablet is 25 mg once a day [12]official. The maintenance dose of Ozempic (semaglutide) is 0.5 mg a week, if needed 1 mg and then 2 mg [13]official. The full table by product: Approved semaglutide dosing.
What the numbers do not tell you. A trial dose shows what was given in a trial, not what dose suits anyone. Milligrams in the injection and the tablet do not match [12]official. The calculator does not open with semaglutide preselected, because the use of an authorised medicine is set out in its product information and by the prescriber. The general calculator's list does include semaglutide, but only to fill in the vial size of powder sold online; that powder is not Ozempic or Wegovy, and the pharmacy pens are not mixed with water.
Semaglutide vs tirzepatide: what is the difference?
In head-to-head trials tirzepatide (Mounjaro) lowered body weight and blood glucose more than semaglutide [14, 15]A.
- Obesity: in SURMOUNT-5, 751 adults without diabetes received the maximum tolerated weekly dose of either tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks. Body weight fell by a mean of 20.2% with tirzepatide and 13.7% with semaglutide. The trial was open-label [14]A.
- Type 2 diabetes: in SURPASS-2, 1,879 people with diabetes received tirzepatide 5, 10 or 15 mg or semaglutide 1 mg a week for 40 weeks. The long-term blood glucose marker HbA1c fell by 2.01 to 2.30 percentage points with tirzepatide and 1.86 percentage points with semaglutide, and weight loss was 1.9 to 5.5 kg greater with tirzepatide [15]A.
- Funding: both comparisons were funded by the maker of tirzepatide [14, 15]A.
More: Tirzepatide (Mounjaro), Liraglutide (Saxenda) and GLP-1 medicines compared.
The most studied combination with semaglutide is CagriSema: cagrilintide and CagriSema.
The situation in the United States
The FDA has warned about unapproved GLP-1 products. It has warned companies that sold semaglutide labelled "for research use", and it is aware of counterfeit Ozempic (semaglutide) [11]regulator.
Is semaglutide legal in Finland?
Yes, as a prescription medicine. Semaglutide is an authorised medicine in the EU, available only on prescription [4, 7, 8]regulator.
- Medicines list. Semaglutide is named as a medicinal substance in the Finnish medicines list (230/2025), so in Finland it is a medicine, not a supplement or a chemical [6]regulator.
- Fimea warning, 29 June 2026. Fimea warned about injectable peptides bought online and sold "for research use only", and advises buying medicines only from legal pharmacies [5]regulator. Semaglutide products that do not come through a pharmacy are not authorised medicines.
- Fakes. In an injectable product, impurities such as endotoxins are a serious risk, and the content can differ from what the label says [5]regulator.
- Prescription and cost. Weight-loss drug cost and prescription. Bringing medicines from abroad: Travelling with peptides. In general: Peptides and the law in Finland.
This is not legal or medical advice. Disclaimer.
Is semaglutide doping?
No, semaglutide is not doping. According to WADA, the status of GLP-1 medicines such as semaglutide is unchanged on the 2027 Prohibited List, because its expert group found the evidence not yet sufficient for inclusion [16]regulator.
FAQ
Is Ozempic the same as Wegovy, since both contain semaglutide?
The active substance is the same, but the products are authorised for different uses. Ozempic (semaglutide) is a type 2 diabetes medicine [7]regulator, and Wegovy (semaglutide) is a weight management medicine [4]regulator. The prescriber decides which product and dose fits.
Ozempic experiences: what do the trials show?
One person's experience does not show how the medicine works for others. In STEP 1, semaglutide 2.4 mg a week lowered body weight by a mean of 14.9% over 68 weeks, against 2.4% with placebo, and 4.5% of the semaglutide group stopped treatment because of gut symptoms [1]A.
What do users themselves report about semaglutide?
In the Reddit accounts of 1345 people we compiled (not research), 912 (68%) reported some benefit and 711 (53%) some harm. The accounts are self-selected and prove neither that it works nor that it is safe: Semaglutide user experiences.
Ozempic side effects: what is reported for semaglutide?
According to the EMA, the most common side effects of Ozempic (semaglutide) are diarrhoea, vomiting and nausea, and serious worsening of diabetic retinopathy is common [7]regulator. With Wegovy (semaglutide), headache, constipation and abdominal pain are also common [4]regulator.
Does Wegovy (semaglutide) cause heartburn?
It can. According to the product information, reflux or heartburn is a common side effect of Wegovy, affecting up to 1 in 10 people. Indigestion and burping are also common [12]official.
Wegovy starting dose: how is the semaglutide dose decided?
The prescriber decides the dose. According to the product information, the Wegovy injection dose is raised gradually over 16 weeks to reduce gut side effects [12]official. In STEP 1 the maintenance dose was 2.4 mg once a week [1]A. More: Approved semaglutide dosing.
Stopping Wegovy (semaglutide): does the weight come back?
In trials it did. In the STEP 1 extension about two thirds of the lost weight had returned within a year [9]A. In STEP 4 those switched to placebo regained 6.9% over 48 weeks [10]A. Talk to your prescriber before stopping.
Semaglutide: where to get it and is a prescription needed?
A prescription is needed. Semaglutide products are available only on prescription from a pharmacy [4, 7, 8]regulator. Fimea warns about injectable peptides sold "for research use only" [5]regulator.
Ozempic vs Mounjaro: which lowers weight more?
In the trial, Mounjaro. In SURMOUNT-5, body weight fell by a mean of 20.2% over 72 weeks with tirzepatide (Mounjaro) and 13.7% with semaglutide. The trial was open-label and funded by the maker of tirzepatide [14]A.
Read the research yourself: sources
Every source opens the original publication or the regulator's page. The level shows what the source itself reports.
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PMID 33567185 A
- Marso SP, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes (SUSTAIN-6). N Engl J Med. 2016;375(19):1834-1844. PMID 27633186 A
- Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). N Engl J Med. 2023;389(24):2221-2232. PMID 37952131 A
- European Medicines Agency. Wegovy: EPAR summary and authorisation details. EMA regulator
- Fimea. Fimea varoittaa: älä käytä verkosta ostettuja pistettäviä peptidejä / Fimea warns: do not use injectable peptides purchased online. 29 Jun 2026. Fimea regulator
- Finland. Lääkeluettelo (Fimea medicines list), 230/2025, annex 1. Finlex regulator
- European Medicines Agency. Ozempic: EPAR summary and authorisation details. EMA regulator
- European Medicines Agency. Rybelsus: EPAR medicine overview and authorisation details. EMA regulator
- Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564. PMID 35441470 A
- Rubino D, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414-1425. PMID 33755728 A
- U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 1 Oct 2026). FDA regulator
- European Medicines Agency. Wegovy: product information (summary of product characteristics and package leaflet), last updated 21 Sep 2026. EMA (PDF) official
- European Medicines Agency. Ozempic (semaglutide): EPAR product information, Annex I summary of product characteristics. Last updated 25 Aug 2026. EMA (PDF) official
- Aronne LJ, et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med. 2025;393(1):26-36. PMID 40353578 A
- Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515. PMID 34170647 A
- World Anti-Doping Agency. WADA publishes 2027 Prohibited List (press release, 21 Sep 2026). WADA regulator
Research sources checked 9-13 Oct 2026. Regulator and registry sources checked 15 Sep to 13 Oct 2026.
Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.
Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.